Why is it important to know the duty cycle of the mode you are using when transmitting?

Answer: B. Some modes have high duty cycles that could exceed the transmitter's average power rating

Modes like FM, RTTY, and many digital modes transmit at full power continuously (high duty cycle). This can exceed a transmitter's average power rating and overheat it, so you may need to reduce power.

Tip: High duty cycle modes can overheat transmitters.